The spinal cord is an ideal system for elucidating the molecular mechanisms that underlie the patterning of different neuronal cell types during embryonic development. Cell-specific transcription plays a central role in restricting neural precursors cells to specific cell fates during development. Recent studies have identified a number of transcription factors that are expressed in restricted populations of neural precursors in the developing spinal cord. These include the paired domain protein Pax6, and the homeodomain proteins Dbx1 and Dbx2, which are expressed in the precursors of two interneuron populations, V0 and V1 interneurons. We will examine the roles Pax6, Dbx2 and Dbx1 play in the specification of V1 and V0 interneuron identify, by analyzing loss of function phenotypes for Pax6 and Dbx2 in the mouse and by misexpressing Dbx1 and Dbx2 in the embryonic chick spinal cord. We will also examine the function of the Hfh2 winged helix transcription factor in the development of V1 interneurons by specifically inactivating Hfh2 in these cells using the Cre/loxP recombination system. These studies will greatly extend our knowledge of how interneuron cell fate is determined in the embryonic spinal cord and will provide insights into the early events that regulate the development of spinal locomotor circuits.